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The earthquake that happened on 27th May 2006 in Yogyakarta and its surrounding caused terrible damageas well as thousands of dead victims. Such an earthquake was caused by horizontal Opak’s Fault activationand it triggered the emergence of Dengkeng’s Fault movement located at the eastern part of the northernOpak’s Fault. To mitigate the disaster that might occur in the future, the channel and the condition underDengkeng’s Fault need to be mapped. One of the methods that could be used to recognize the under surfacecondition is the gravity method which is based on the measurement of gravity field variation on the earth’ssurface. The existence of a fault would change the condition of rocks in such fault channel zone so that itinfluences the local gravity change. Therefore, on this opportunity, research of Dengkeng’s Fault is carriedout using the gravity method. The measurement of the gravity field has been done in 94 points using LacosteRomberg Gravitymeter type G-1118 MVR. The height of the measurement point was measured usingGPS Altus APS-3 differential, and the research coordinate was measured using GPS Garmin III Plus. Dataon the gravity field that had been obtained was corrected so that complete anomaly Bouguer (ABL) isobtained. Further, the regional component of the ABL value is separated from its local component using anupward continuation method. The target that would be identified is shallow so that the local anomaly thatwould be analyzed uses the second vertical derivative (SVD) and modeled in 3 dimensions using OasisMontaj software. Second vertical derivative type of fault. 3-dimensional modeling was used to identify theunder surface structure of the research area comprehensively. The result of the analysis using the secondvertical derivative shows that Dengkeng’s Fault is a strike-slip fault with the west-east direction. To clarifythe under the surface condition from the 3-dimensional modeling, incisions were made to the Z-axis direction(vertically) and X-axis direction. Z-axis direction modeling shows that the fault in the research area starts tobe seen at the depth of 500 meters to 3500 meters to the west-east. X-axis direction modeling shows that thefault was located at Easting 444500 meter and Northing 9141000 meters to the Easting 456250 and Northing9139000. Based on the modeling result, it could be seen that the southern part block of Dengkeng’s movedto the east, while the northern part block moved to the west.

Research on Lasem fault modeling has been carried out to analyze the location of the Lasem fault indication. The Lasem fault is indicated in 3 zones, namely the Rembang zone, Randublatung depression zone and Semarang-Rembang depression zone. Lasem fault is a fault located in the Pati-Rembang area which is an active fault and is close to the Semarang area. This research uses the gravity method as a basic understanding. The data uses obtained through the TOPEX/POSEIDON website. The data obtained were 154 measurement points at coordinates 111000' BT (E)-111013' BT (E) and 6040' LS (S)-6050' LS (S). The results obtained on TOPEX/POSEIDON are data of latitude and longitude coordinates, elevation and free air anomaly correction values. After that, further correction is made in the form of bouguer correction and terrain correction so that the complete bouguer anomaly value is obtained. The complete bouguer anomaly data is analyzed by spectrum with the results of depth estimation for the anomaly. Then an upward continuation is carried out to separate regional anomalies and residual anomalies. After that the gradient analysis filter, eulerdeconvolution, 3D and 2D modeling are done. Gradient analysis filter in the form of first horizontal gradient with the results in the form of fault indications and second vertical derivatives to determine the type of fault that is strike-slip fault. Euler deconvolution is used to determine the estimated subsurface depth with yields of up to 5000 m below sea level. 3D modeling is carried out to see fault indications which result that faults can be seen from depths of 1200 m to 4000 m. 2D modeling results show the types of rocks in the form of claystone, sandstone, limestone, and andesite, respectively the rocks have a density of 2.21 gr/cm 3 , 2.35 gr/cm 3 , 2.55 gr/cm 3 and 2.6 gr/cm 3. Keywords-Lasem fault, gravity method, gradient analysis, euler analysis, 3D and 2D modeling.. I. INTRODUCTION The gravity method is one of the geophysical methods based on the measurement of small variations in a gravity field. The difference in small variations or deviations in the terrain from point to point above the surface of the earth, is caused by lateral variations [1][2]. The gravity method is a method that studies variations in the gravity field that occur by variations in the density of rock masses below the surface, so that the variation investigated is the difference in the gravity field from an observation point to another point [2][3]. The gravity method can be used in analyzing the presence of the lasem fault by looking for the density variable that is below the surface. Lasem Fault is a fault with the longest straightness, occupying a depression with axes trending southwest-northeast. In previous research which concluded that by doing inversion modeling from gravity data concluded that the Lasem fault lies in 3 zones, namely the Rembang zone, the Randublatung depression zone and the Semarang-Rembang depression zone. Then the inversion modeling results obtained are depression models in the...

Cekungan Akimeugah merupakan salah satu cekungan di Papua yang memiliki cadangan minyak besar (giantfield).  Kajian tahap awal mengenai potensi di Cekungan Akimeugah adalah penyebaran anomali permukaan.  Identifikasi penyebaran anomali permukaan dapat dilakukan menggunakan metode penginderaan jauh dengan memanfaatkan data Citra Landsat-8 OLI dan ketinggian data DEMNAS.  Hasil dari pengolahan data citra satelit Landsat-8 terdapat 5 kelas klasifikasi untuk hasil citra NDVI dengan rincian nilai -1 - (-0,16078) dapat diindikasikan tidak terdapat vegetasi, batuan tandus atau badan air.  Nilai NDVI dengan rentang 0,30 – 0,45 dapat diidentifikasikan di daerah tersebut kerapatan vegetasinya rendah dan vegetasinya dapat berupa seperti semak belukar, padang rumput, tanaman tua, ataupun tanaman yang stres.  Nilai +1 yang merupakan pariwisata di daerah tersebut sangat tinggi  Hasil yang diperoleh dari pengolahan data DEMNAS adalah kelurusan dominan pada daerah penelitian sebesar 43,2 atau 223,2 arah timur laut - barat daya.  Terdapat 16 wilayah dengan sebaran nilai densitas kelurusannya tinggi hingga sangat tinggi yaitu 158.529524 - 242.066040.  Wilayah dengan densitas kelurusan yang tinggi, terdapat struktur antiklin dan berada di formasi yang mungkin adalah wilayah dengan nomor 4,11 dan 14. Nomor 4 yang berada di wilayah Kegata, nomor 11 berada dalam cakupan wilayah Deiyai dan nomor 14 yang berada di wilayah Tembagapura dan  Kabupaten Mimika.

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